The present invention relates to a centering arrangement and more particularly, to a centering arrangement of a drilling machine or the like mounted on a boom or jib structure which is loaded on a truck or the like, in which arrangement, a drilling pattern obtainable on a temporarily provided drilling pattern on a drilling pattern plane in a rectangular coordinate system and which is based on the position of the drilling machine is adjusted to an actual drilling pattern on a working plane corresponding to the actual working face for centering of the drilling machine without mechanically moving the position of the truck.
Conventionally, when a tunnel or the like, for example, is excavated by a drilling machine such as machine drill, i.e., rock drill, rock borer, etc., mounted on a boom structure, it is first necessary to bring a reference point of the boom structure in a drilling pattern plane in rectangular coordinate system into coincidence or superposition with a reference point in a working plane in a rectangular coordinate system for drilling according to the drilling pattern on the drilling pattern plane. Accordingly, it has been conventional practice to lift the truck loaded with the boom structure by a jack or the like or to mechanically slide the position of such truck for centering of the drilling machine. The known centering practice as described above, however, has disadvantages in that considerable time as well as special skill are required to mechanically move the position of the truck for correction, with insufficient centering accuracy, and power separate from that for the boom is required for such mechanical movement, resulting in high cost of the centering operation.